iPhone 6 is rumored to feature bigger displays, compared to the current versions of the device. Photo: Concept by Martin Hajek

Rumors that Apple Inc. (NASDAQ:AAPL) is facing serious issues related to production of the new iPhone 6 models have resurfaced, with one analyst predicting that the company could end up releasing only one version of the new and bigger iPhone this year, while the other model could be delayed until next year.

Apple is said to be having trouble with the new in-cell touchscreen panel as well as with uneven colors on the phone's metal casing, which could hinder the company’s iPhone release plans for this year, Ming-Chi Kuo, an analyst at KGI Securities, said in a new report, adding that only the 4.7-inch version of the iPhone 6 will be launched this year, and that the bigger 5.5-inch model could be pushed back to 2015.

“Production bottlenecks on 4.7-inch iPhone 6 center on the yield rate of in-cell touch panel and metal casing,” Kuo said in the report, obtained by MacRumors. “As in-cell touch panel becomes larger in size, the edge of the panel may become insensitive to touch. Meanwhile, under new manufacturing process for the iPhone 6 metal casing, color unevenness is an issue.”

Kuo, who has said that Apple is facing similar issues with the smaller version of the next iPhone, believes Apple will overcome them in time for a September release. However, on the larger 5.5-inch iPhone 6, the issues could be far worse when combined with past problems associated with the model, such as the production of sapphire displays. In addition, Kuo said that the new 5.5-inch scratch-resistant front panel is not likely to “pass the drop test near term,” and could also prompt launch delays.

Kuo has also predicted that, if Apple delays the launch of the 5.5-inch iPhone 6 to 2015, the company may cut the price of the existing iPhone 5s and iPhone 5c, to help increase Apple’s sales in the holiday quarter, along with the new 4.7-inch version of the iPhone 6.

At the same time, the analyst said that there is a really slim chance that Apple might manage to release the 5.5-inch iPhone 6 launch this year. However, if that happens, it would see the light of day only after mid-November, much later than Apple’s typical iPhone release schedule, Apple Insider reported.

Rumors have it that Apple could launch the new 4.7-inch iPhone 6 on Sept. 19 as the date suits Apple’s traditional iPhone-release cycle and supports similar claims made by Deutsche Telekom, a German wireless provider, in May. If Kuo’s predictions turn out to be accurate, the 4.7-inch iPhone 6 could be announced on that day.